Programmable logic devices (PLDs), such as for example complex programmable logic devices (CPLDs) and field programmable gate arrays (FPGAs), utilize various types of memory to store their configuration data, which defines the functionality of the PLD. For example, CPLDs generally employ electrically erasable complementary metal oxide semiconductor (EECMOS) technology, which is non-volatile but can be programmed (e.g., receive and store data) only a limited number of times and takes longer to program than some other types of memory (e.g., static random access memory (SRAM)). CPLDs typically provide numerous benefits, such as fast, predictable timing and single-level, wide-logic support.
As another example, FPGAs typically provide benefits, such as high logic density and low standby power and generally utilize SRAM technology. SRAM is infinitely reconfigurable, but loses its programming upon power loss (i.e., volatile memory) and generally requires an external non-volatile source to supply it with configuration data upon power-up.
Various types of non-volatile technology have been introduced for FPGAs to replace SRAM. For example, antifuse-based technology provides non-volatility, but can not be reprogrammed and so is not reconfigurable. Other types of non-volatile technology have been introduced, but typically suffer from various drawbacks, such as limited programmability.
Furthermore, conventional PLDs generally provide a limited number of ways to program internal memory. For example, a PLD employing EECMOS technology (e.g., electrically erasable programmable read only memory or EEPROM) may be programmable only through a JTAG interface. As a result, there is a need for improved programmable logic devices and techniques for programming the programmable logic devices.